What are proteins primarily comprised of?

Proteins are primarily comprised of amino acids, which are organic compounds made up of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur. These amino acids are linked together in chains to form proteins through peptide bonds in a process known as translation. Each protein's unique sequence of amino acids determines its specific structure and function, allowing for the vast diversity of proteins with various roles in biological processes, including enzyme activity, structural support, and regulation.

In contrast, nucleotides are the building blocks of nucleic acids like DNA and RNA, fatty acids are key components of lipids, and sugars are carbohydrates used primarily for energy storage and structural functions in cells. Hence, while they are important biological molecules, none of these alternatives serve as the basic building blocks for proteins.